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Fig. 6. Comparison of periodic heartbeat traces of first with third heart segment
in D. hydei (male 4). (A) Sensor beside the waist at the transition
of the first heart segment to the aorta. The mean IR-transmittance is
decreasing during retrograde pulsations, when no hemolymph is pumped through
the aorta. Pulses, probably of the intestine, with a lower frequency are
superimposed on the heart pulses (arrows). (B) Same individual, with sensor
beside the third heart segment the next day. Mean IR-transmittance is
increasing during retrograde pulsations, when hemolymph is accumulating in the
abdomen.